RÉSUMÉ
BACKGROUND: The endosomal-lysosomal and autophagy (ELA) pathway may be implicated in the progression of Alzheimer's disease (AD); however, findings thus far have been inconsistent. OBJECTIVE: To systematically summarize differences in endosomal-lysosomal and autophagy proteins in the cerebrospinal fluid (CSF) of people with AD and healthy controls (HC). METHODS: Studies measuring CSF concentrations of relevant proteins in the ELA pathway in AD and healthy controls were included. Standardized mean differences (SMD) with 95% confidence intervals (CI) between AD and healthy controls in CSF concentrations of relevant proteins were meta-analyzed using random-effects models. RESULTS: Of 2,471 unique studies, 43 studies were included in the systematic review and meta-analysis. Differences in ELA protein levels in the CSF between AD and healthy controls were observed, particularly in lysosomal membrane (LAMP-1: NAD/NHCâ=â348/381, SMD [95% CI]â=â0.599 [0.268, 0.930], I2â=â72.8%; LAMP-2: NAD/NHCâ=â401/510, SMD [95% CI]â=â0.480 [0.134, 0.826], I2â=â78.7%) and intra-lysosomal proteins (GM2A: NAD/NHCâ=â390/420, SMD [95% CI]â=â0.496 [0.039, 0.954], I2â=â87.7%; CTSB: NAD/NHCâ=â485/443, SMD [95% CI]â=â0.201 [0.029, 0.374], I2â=â28.5%; CTSZ: NAD/NHCâ=â535/820, SMD [95% CI]â=â-0.160 [-0.305, -0.015], I2â=â24.0%) and in proteins involved in endocytosis (AP2B1:NAD/NHCâ=â171/205, SMD [95% CI]â=â0.513 [0.259, 0.768], I2â=â27.4%; FLOT1: NAD/NHCâ=â41/45, SMD [95% CI]â=â-0.489 [-0.919, -0.058], I2 <0.01). LC3B, an autophagy marker, also showed a difference (NAD/NHCâ=â70/59, SMD [95% CI]â=â0.648 [0.180, 1.116], I2â=â38.3%)), but overall there was limited evidence suggesting differences in proteins involved in endosomal function and autophagy. CONCLUSION: Dysregulation of proteins in the ELA pathway may play an important role in AD pathogenesis. Some proteins within this pathway may be potential biomarkers for AD.